1. Field of Invention
The present invention relates to a variable compression ratio engine that varies a compression ratio, improving combustion efficiency, reducing noise/vibration, and increasing output by varying the compression ratio of the combustion chamber in accordance with the driving status.
2. Description of Related Art
In general, the thermal efficiency of heat engines increases when the compression ratio is high, and in spark ignition engines, the thermal efficiency increases when the ignition timing is advanced up to a predetermined level.
However, when the ignition timing is advanced with a high compression ratio in the spark ignition engines, abnormal combustion is generated and the engines may be damaged, so that there is a limit in advance of the ignition timing and accordingly the output is necessarily reduced.
A VCR (Variable Compression Ratio) apparatus is an apparatus that changes the compression ratio of a gas mixture in accordance with the operation state of an engine. According to a variable compression ratio engine that varies the compression ratio, it improve the fuel efficiency by increasing the compression ratio of a gas mixture under a low load condition and prevents knocking and improves the output by reducing the compression ratio of the gas mixture under a high load condition.
The existing variable compression ratio engines that are designed to vary the compression ratio change the compression ratio by changing the distance between the crankpins connecting the crankshaft with the pistons.
Those types of variable compression ratio engines that vary the compression ratio include a control shaft, a shaft cap, a block cover, and a control motor, in which the control motor rotates the control shaft and the driving arm on the control shaft rotates an eccentric bearing through a link. The shaft cap is needed to fix the engine block to the control shaft and is covered with the block cover, such that the number of parts increases and the weight increases accordingly.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.